A particular problem in the field of hair treatment is that of how to deliver benefit agents to the hair from “rinse-off” products like shampoos and conditioners, the problem simply being that a substantial proportion of the benefit agents may be washed away with the rinse water.
Benefit agents include such things as conditioning agents, perfumes, colorants, feel modifiers, lustrants, sun screens, nutrients, moisturisers, styling agents and medicinal agents (such as germicides, antidandruff and anti-pruritic agents).
Two methods are commonly used to enhance the deposition of benefit agents onto hair.
One method is to use large droplets of oil carrying a benefit agent in a shampoo or conditioner base. This method relies on physical contact between the hair and the droplets, followed by spreading of the oil droplets over the hair surface. This can, however, lead to the hair feeling greasy or heavy, and looking dull and lifeless because of the extensive spreading of the oil and its absorption by the hair.
Another method is to employ a deposition polymer, which is usually a cationic deposition polymer. Such systems rely solely on electrostatic attractive forces between oppositely charged species. This means in practice that other insoluble materials may be indiscriminately deposited onto the hair. This can lead to dulling of the hair, loss of shine and also to a heavy feel for some consumers.
There is a need for hair treatment compositions which provide for deposition and delivery of benefit agents to hair in a more efficient and targeted manner.
The present inventors have found that this problem can be solved by the use of certain hair substantive polymers which are able to interact specifically with the protein surface of the hair fibre.